Conventional doping processes normally involve introduction of an impurity material (e.g., a dopant) onto the surface of a semiconductor substrate. This dopant material is usually deposited onto, or implanted into, the surface of the substrate, and then diffused into the substrate to a predetermined depth by a process commonly called “drive-in diffusion.” Depending on the type of dopant material used, the doped substrate can be made n-type (using donors) or p-type (using acceptors).
In some instances, implantation of dopant species, such as by ion beam implantation, may undesirably damage the crystal structure in the surface region of a semiconductor substrate. It may be desirable to instead deposit a thin (˜angstroms) layer of dopant material on the surface of the substrate, and then apply heat to the substrate to diffuse the dopant material. This heating process can require heating the entire substrate in a furnace at high temperatures for fixed time periods. As semiconductor device dimensions become smaller, however, more flexible alternatives are needed that will achieve desired doping of substrates without the potential for damage either by implantation or high temperature bulk heating and diffusion treatments.